This invention relates generally to digital computer systems and more particularly to requestor (e.g., central processing unit) -memory systems.
Present day computer systems are constructed on a modular basis. That is, in a digital computer system requestor modules and memory modules are put together to form the requestor-memory system. In a modular digital computer of this sort a cabinet or other host apparatus is wired to accept standard modules, as for example standard memory modules. Modules then need to be standardized to fit in any appropriate position in the wired cabinet. That is there must be substitutability between the standard modules. A standard memory module needs to work just as well in a first location wired for a standard memory module as in any other location wired for that standard memory module.
Another key element in present day digitial computer systems is expandability. Memory modules may be of many different sizes. For example, a single memory module may have a total capacity of 264,144 words (hereinafter generally referred to as 256,000 words). However, that same memory module may be available in smaller versions, as for example 65,256 words (hereinafter generally referred to as 64,000 words) or 134,072 words (hereinafter generally referred to as 128,000 words) versions. If these memory modules are dependent upon where they are placed in the overall requestor memory addressing scheme, then a different version of a standard memory is needed for each position. If the memory module is position dependent, then the memory modules are not available for relocation in different positions in the wired cabinet. This would eliminate such common and needed techniques as troubleshooting, preventive maintenance and reduced capacity fail-soft operations.
The addressing structure of the requestor-memory system must be able to accommodate memory modules of different sizes at different locations and, conversely, memory modules, in order to be standardized, must accommodate the addressing scheme available at any appropriate location within the wired cabinet. That is, a 64,000 word memory must be able to operate in any location within the cabinet wired to accommodate a 64,000 word memory. The memory module must not be dependent upon where it is located within the physical wired cabinet location and hence the position in the overall requestor-memory addressing scheme.